Amp/Headphone distortion

What is the relationship between amp and headphone distortion? For amps we know that, as you push the amp more you start noticing harmonic distortions. Could this be more so with weaker amps than the higher power amps? Although, you can get a headphone to a loudness based on specs, but distortion is another, correct?

Is it true that SS amps only distort significantly at the point at when it starts clipping? Isn't there a non-linear zone as you push the amp?

What is the relationship between amp and headphone distortion? For amps we know that, as you push the amp more you start noticing harmonic distortions. Could this be more so with weaker amps than the higher power amps? Although, you can get a headphone to a loudness based on specs, but distortion is another, correct?

Is it true that SS amps only distort significantly at the point at when it starts clipping? Isn't there a non-linear zone as you push the amp?